Friedreich's ataxia (also referred to as FA or FRDA) is a rare but fatal autosomal recessive neurodegenerative disease, with an estimated incidence of 1 in every 40,000 people. This condition is typically found in individuals with European, Middle Eastern, or North African ancestry. FRDA causes progressive damage to the nervous system and muscle cells, resulting in a loss of coordination as well as various neurological and cardiac complications. In particular, FRDA patients develop neurodegeneration of the large sensory neurons and spinocerebellar tracts, as well as cardiomyopathy and diabetes mellitus. Onset of symptoms is typically seen between the ages of 5 and 15 years, and the mean age of death is approximately 38 years.
Friedreich's ataxia is caused by an abnormal expansion of the guanine-adenine-adenine (GAA) trinucleotide repeat sequences in intron 1 of the frataxin (FXN) gene, resulting in transcriptional repression and reduced expression of the frataxin (FXN) protein. Frataxin, which is encoded by the nuclear frataxin (FXN) gene, is a highly-conserved, 210-amino acid protein that is localized to the mitochondrion. Most FRDA patients (approximately 98%) carry a homozygous mutation characterized by an expansion of a GAA trinucleotide repeat in the first intron of the frataxin (FXN) gene. Pathological GAA expansions can range from about 66 to more than 1,000 trinucleotide repeats, whereas frataxin alleles that are not associated with FRDA comprise from about 6 to about 34 repeats.
There is presently no cure for FRDA or specific therapy to prevent progression of the disease which has been approved for use as a treatment. Therefore, there is a need to develop compositions that restore or partially restore frataxin levels to treat and/or prevent FRDA.